Double-sided flip-chip mounted connection structures are known in which IC chips (Integrated Circuit Chips) are flip-chip mounted onto the respective front and rear surfaces of a wiring substrate with an anisotropic conductive adhesive film (ACF) or a non-conductive adhesive film (NCF) interposed therebetween. Such a double-sided mounted type connection structure is made in a manner such that the ACF or NCF is temporarily affixed onto one surface of the wiring substrate; an IC chip is aligned and temporarily mounted thereon and then subjected to thermal pressure bonding for flip-chip mounting with a heating and pressing tool; and then, another IC chip is flip-chip mounted onto the other surface in the same manner.
However, there arose a problem that the first flip-chip mounting on the one surface caused warpage not only on the wiring substrate but also on the IC chip itself; the another IC chip was aligned with reduced accuracy when the another IC chip was flip-chip mounted onto the other surface; and the IC chips were difficult to be accurately subjected to thermal pressure bonding with the heating and pressing tool. This problem has become noticeable as the IC chip and the wiring substrate have been increasingly reduced in thickness in recent years.
It has been thus practiced to flip-chip mount the IC chips not on one surface and then the other surface in sequence but on both the surfaces at a time. That is, it has been suggested that the thermosetting anisotropic conductive adhesive film (ACF) or non-conductive adhesive film (NCF) is temporarily affixed onto each of the front and rear surfaces of the wiring substrate, and then the IC chips are each temporarily mounted thereon to prepare a half-finished connection structure; the half-finished connection structure is subsequently placed on a placement receiving base which has a placement surface made of a rubber material or the like and which has heating means; and then while the half-finished product is being heated from the side of the placement receiving base, the IC chips on the front surface are pressed with a pressure applying tool having an elastic pressing surface (Patent Literature 1).